Install Quadro driver and it will recognize the 980 as well as provide some functions you would need for running Davinci resolve. BTW I have a Quadro K420 as well as an intensity 4k I would be willing to sell cheap. PM if interested.

That will work, but you can probably just put both cards in right away. If they don't find the right driver, they will use the windows driver. You may have to boot twice whenever you make a physical change. The 980 has to go in a 16x slot. The display will run off of the lowest number slot while you are setting up. If necessary you can plug the display into the 980 while setting up and switch later, however you probably won't see any boot screens until windows is loaded. You can switch display cards at will, should you ever need to go into your bios setup.

There should be no issues with Premiere and it will use the GPU on both cards. Whether you get 10 bit 444 or RGB with the Nvidia driver depends on the right card, display and cable combination. If you get everything to work the way you like, you can calibrate using any tool you like through the system.

The blackmagic card should pretty much give you 10 bit on any display capable of it but you need to put up with flaky BM software and there seems to be only 1 choice as a calibration system. It will run in a 2x slot.

I have used both in premiere successful but have never been able to get 100% calibration other than visually using the display hardware. I would say try the Quadra and if you can get the color you want, it will be more flexible with Premiere.

For resolve, a BM card or equivalent is the only way to go for dual display. If you want to run resolve even as single with the Quadra and 980, use the Nvidia control panel to disable the GPU on the Quadra and then also do that within Resolve.

Good luck.